Number One: Remember that there is always somebody that cares about you or somebody that can help you! Do not give up thinking that nobody cares for you. Even if it seems like nobody loves you, it is simply not true, and suicide always leads to pain for those who love you.
You must seek help as soon as possible, so I will give you some examples of who can help:
You can call the National Suicide Helpline at 1-800-273-8255 if you are in the United States. If you are not in the United States, here is a link with the hotline in various other countries: http://ibpf.org/resource/list-international-suicide-hotlines.
You can go to the emergency room. They take mental health seriously just like physical injuries, and they will ensure that they find somebody who can give you the care and advice you need.
You can also talk to a therapist, psychiatrist, or psychologist, but you may not be able to get immediate help, so I would recommend getting more immediate help first and then finding a therapist you can talk with on a regular basis.
You can talk to a friend, family member, or counselor that you can trust.
My friend, please, DO NOT attempt to commit suicide. It may seem like it's an option that is good for you at times, but there is always light at the end of the tunnel. Giving up on life only keeps you from reaching this light. If you don't know of anybody that you have a relationship with that you feel comfortable talking to, remember to call that hotline I recommended you before: 1-800-273-8255.
Remember, there are more people that care for you than you could ever imagine, and suicide is never the answer.